1. Field of the Invention
This invention relates generally to heating elements and such for deicing surfaces exposed to severe cold.
2. Description of Related Art
The following art defines the present state of this field:
Watson, U.S. Pat. No. 223,784 describes castings formed in sections, connected by curved pipes, in combination with the enclosed pipes and connections arranged to serve as a pavement for sidewalks or streets or both.
Custer, Jr., U.S. Pat. No. 2,844,696 describes a melting mat comprising a sheet of electrically insulative material having an electrically conductive heating coil embedded therein, a heat conductive wire mesh overlying said sheet, a tread of electrically insulative material positioned over said wire mesh and bonded to said wire mesh and said sheet sandwiching said wire mesh between said tread and said sheet, metallic ground strips secured to said mat, said wire mesh being connected to said ground strips.
Jamison, U.S. Pat. No. 2,912,555 describes a heated surface covering device for multiple use in overlying and in end to end relation to form walkways, driveways, roadways or the like, comprising a flat molded rectangular plastic body having parallel upper and lower faces, a non-plastic heater element molded into the body to extend for the major width and length thereof, the heater clement comprising a rectangular sheet of stiff and relatively thick insulating board, the board at its opposite ends being provided with spaced apart perforations, a plurality of strands of an electrical conductor that are connected to the sheet and that extend longitudinally of the sheet and with the strands overlying the upper surface of the sheet in spaced apart parallel relation and whereby the major heat from the strands is directed toward the surface of the plastic body, the strands being threaded through the apertures at the opposite ends of the sheet, the said sheet insulating the lower surface of the body against the escape of heat downwardly from the contended through one marginal edge of the plastic body adjacent one end for connection to a source of electrical energy, the said body portion at its opposite ends being transversely reduced in thickness to form flat tongue for the full transverse width of the slabs and whereby the tongues have overlapping engagement with the tongues or adjacent bodies, each of the bodies inwardly from their reduced ends being vertically apertured for the passage of anchoring pins that are driven downwardly into an underlying surface to prevent shifting of the bodies with respect to each other and with respect to an underlying surface, all of the slabs and their projecting conductors being energized and heated from a common source of electrical energy.
Bayless et al., U.S. Pat. No. 4,967,057 describes individual electrically heated mats, self-regulated by use of an electrical element whose resistance varies proportionately with its temperature, used for covering walking areas to prevent accumulation of snow and ice. Each mat is provided with male and female electrical connections on the ends of short power cords to permit any number of mats to be chained together in electrical parallel and to be used to cover, for example, a flight of stairs by positioning one mat on each stair.
Shields, U.S. Pat. No. 5,591,365 describes a heating apparatus for preventing the accumulation of snow and ice, and having an apertured heating mat in the form of a lattice or web. The heating mat is made of a durable weatherproof insulative polymer so that the mat may be installed on any outdoor surface, such as a driveway, walkway, or rooftop. The apertures within the lattice serve to increase the flexibility of the mat, thus allowing the mat to fit uneven surfaces. In addition, this flexibility allows the mat to be easily rolled up when not in use, the apparatus therefore only occupying minimal storage space. The heating mat is also constructed to be highly resistant to wear and may be left outdoors for the entire snow season, exposed to both the elements and frequent vehicular traffic without losing its effectiveness. Also included is;a controller from which the apparatus can be set to a manual mode, in which the apparatus may be manually activated, or an automatic mode, in which the apparatus is automatically activated by snowfall.
Saylor, U.S. Pat. No. 5,614,292 describes a thermal walkway cover comprising at least three laminated layers including a middle layer of electrically conductive carbonized rubber, a durable, waterproof, UV-resistant top layer, and an insulating, waterproof bottom layer. Means are provided in to form of electrically conductive strips embedded in the middle layer to heat the middle layer. Connections are provided to a power source. The cover may have one or more edges of a dovetail construction so that cover sections or modules may be connected together to cover a desired walkway area, in which case electrical connections are provided between individual modules.
The prior art teaches the use of buried heating strips for heating rooms, driveways, air strips and other applications, but does not teach the present specific combination of elements which provide advantages as described in the following summary.
The present invention teaches certain benefits in construction and use which give rise to the objectives described below.
A deicing apparatus comprises an integral stack of layers inseparably joined in intimate mutual contact forming a flexible mat. The layers include a first layer to be placed into contact with a surface to be deiced or to be maintained clear of ice, having electrical insulation properties, a second layer of resistance heating, electrically conductive material formed in an electrical conducting path, a third layer of electrically insulating material, a forth heat energy reflective layer of metallic foil, and a fifth layer of thermally insulative and physically tough material. A device for applying an electrical current to the second layer to produce heat energy is provided.
A primary objective of the present invention is to provide an apparatus and method of use of such apparatus that provides advantages not taught by the prior art.
Another objective is to provide such an invention capable of deicing an area around an automobile tire.
A further objective is to provide such an invention capable of deicing a handle and lock on an automobile door.
A still further objective is to provide such an invention capable of use with 12-volt dc or 115-volt ac power sources.
Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.